This invention relates to lightweight trailers. More particularly, it relates to kingpin assemblies for lightweight trailers. Herein, xe2x80x9clightweight trailersxe2x80x9d includes aluminum alloy trailers, magnesium alloy trailers and other trailers that are primarily made from a material that is lighter in weight than steel and steel based alloys.
It is known to provide lightweight trailers with steel kingpins. For example, U.S. Pat. No. 3,600,005, granted Aug. 17, 1971, to Gordon K. Glaza, and assigned to The Dow Chemical Co., discloses a steel kingpin mounted in a support frame that is a part of the under frame of a trailer. The support frame is constructed from a lightweight metal such as an aluminum or magnesium alloy. The kingpin has an inner end portion that extends through an opening in the support frame and includes a threaded upper end that threads into a threaded opening in a cap. When the kingpin and the cap are connected together a flange that is intermediate the length of the kingpin presses against a lower portion of the under frame and the cap presses against an upper portion of the under frame.
Canadian Patent No. 1,260,037, granted Sep. 26, 1989, to Donald B. Stinson, and assigned to the Fruehauf Corporation, discloses a second way of constructing a lightweight undercarriage frame and a second way of connecting a steel kingpin to the undercarriage frame.
There is a need to provide a kingpin assembly for lightweight trailers, e.g. aluminum alloy trailers, that has a minimum of welds so that the amount of heat that is transferred into the assembly is reduced. This is important because when an aluminum alloy is welded, it loses a portion of its original properties. A principal object of this invention is to fill this need.
A principal object of the present invention is to provide an improved kingpin assembly which is lightweight, but strong and durable, is easily maintained, and which can be used universally in several aluminum alloy trailer configurations. The number of welds are reduced by making the undercarriage frame from extrusions of a unique design which requires a minimum of welds and which place the welds in a low stress area of the kingpin assembly.
The present invention includes providing an aluminum frame member that includes a bottom and a kingpin receiving opening in the bottom. An aluminum kingpin mounting block is provided that includes a downwardly opening socket surrounded by a base. A steel kingpin is provided that has a kingpin head that is positioned within the socket and a kingpin shaft that depends from the kingpin head and downwardly from the socket. A plurality of fasteners detachably connect the kingpin head to the aluminum kingpin mounting block when the kingpin head is within the socket. The kingpin shaft extends downwardly from the kingpin head and through the kingpin opening in the bottom of the aluminum frame member. The kingpin shaft projects downwardly from and below the aluminum frame member. The aluminum kingpin mounting block is welded to the aluminum frame member, for securing the aluminum mounting block and the steel kingpin to the aluminum frame member. The aluminum frame member comprises a pair of longitudinally spaced apart transverse box beams that extend upwardly from the bottom of the aluminum frame member. The kingpin opening in the bottom is located between the transverse box beams. The aluminum mounting block is welded to the transverse box beams.
The aluminum frame member comprises two extrusions that are welded together to form the aluminum frame member. Each extrusion comprises a portion of the bottom of the aluminum frame member and a different one of the transverse box beams. The portions of the extrusions which provide the bottom of the aluminum frame member are welded together between the transverse box beams.
In preferred form, each box beam is composed of at least three, horizontally spaced apart, vertical webs with lower edges that are attached to the bottom of the aluminum frame member. The vertical webs also have upper edges and the box beam includes a top web that is connected to and interconnects the top edges of the vertical webs.
According to another aspect of the invention, a pair of longitudinal, aluminum frame beams are interconnected between the two transverse box beams, on opposite sides of the aluminum mounting block. The longitudinal frame beams are connected to the bottom of the aluminum frame member and at their ends are welded to the transverse box beams.
In preferred form, the aluminum kingpin mounting block and the kingpin head are provided with complementary, circular arrays of fastener openings, and the fasteners extend through these openings. Also, in preferred form, the fasteners are studs that are press fit into the openings in the mounting block. The studs have threaded lower end portions that project downwardly from the aluminum kingpin mounting block and through the openings in the kingpin head. The fasteners further include nuts that are threaded onto the threaded lower ends of the studs.
The present invention also includes providing the kingpin assembly with a stainless steel plate that is positioned between the aluminum kingpin mounting block and the head of the steel kingpin.
Another aspect of the present invention is the provision of a replaceable, stainless steel wear plate below the bottom of the aluminum frame members. Preferably, screw fasteners are used for securing the stainless steel wear plate to the aluminum frame member. Some of the screw fasteners may screw into the aluminum kingpin mounting block. Others may screw into nut-like elements that are secured to upper surface portions of the bottom of the aluminum frame member.
Other objects, advantages and features of the invention will become apparent from the description of the best mode set forth below, from drawings, from the claims and from the principles that are embodied in the specific structures that are illustrated and described.